#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30

void error_handling(char *message);

#define PORT "8888"

int main(int argc, char *argv[]) {
    int serv_sock;
    char message[BUF_SIZE];
    int str_len;
    socklen_t clnt_adr_sz;

    struct sockaddr_in serv_adr, clnt_adr;
//	if(argc!=2){
//		printf("Usage : %s <port>\n", argv[0]);
//		exit(1);
//	}

    serv_sock = socket(PF_INET, SOCK_DGRAM, 0);
    if (serv_sock == -1)
        error_handling("UDP socket creation error");

    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_adr.sin_port = htons(atoi(PORT));

    if (bind(serv_sock, (struct sockaddr *) &serv_adr, sizeof(serv_adr)) == -1)
        error_handling("bind() error");

    while (1) {
        clnt_adr_sz = sizeof(clnt_adr);
        str_len = recvfrom(serv_sock, message, BUF_SIZE, 0,
                           (struct sockaddr *) &clnt_adr, &clnt_adr_sz);
        sendto(serv_sock, message, str_len, 0,
               (struct sockaddr *) &clnt_adr, clnt_adr_sz);
    }
    close(serv_sock);
    return 0;
}

void error_handling(char *message) {
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}
